Help needed on adding torsional loading

I am trying to use solidworks to validate torsional stress of a solid bar with fillet (pleases see the attached snapshot). I fixed the end of bigger diameter.

I applied a torque to the end of smaller shaft. Now here is what I am not sure of as to how to apply the torque. The way I did is to select the end-section of the small shaft as the "faces for torque". and I selected the cylindrical surface of the bigger shaft for the "direction".

After running the study, the graph of the stress looks funny. Somehow, the smaller shaft bended. I was expecting to have twisted shaft because of the pure torsion.

Please give me the right direction. How exactly can I get the pure torsion?